The present invention relates to an image forming apparatus capable of forming an image in colors. Further, the present invention relates to a method of adjusting color balance applied to the image forming apparatus.
In a conventional image forming apparatus, a toner image as a developer image is formed on a photosensitive drum, and the toner image is transferred to a printing medium or a transfer medium such as a transportation belt. Such a conventional image forming apparatus includes a printer of an electro-photography type, a facsimile, a copier, or a multi function product having three functions of the facsimile, the copier, and the printer.
The conventional image forming apparatus may have a capability of forming an image in colors. In the conventional image forming apparatus, it is necessary to accurately adjust color balance for obtaining a color image with high quality.
In the conventional image forming apparatus, in order to accurately adjust color balance, it may be configured to control an energy amount of a static latent image forming unit and an energy amount of a developing unit (refer to Patent Reference).
Patent Reference: Japanese Patent Publication No. 2004-258281
In this case, the energy amount of the static latent image forming unit represents an energy amount of light irradiated on a photosensitive drum. More specifically, the energy amount is represented with an exposure time during which a light irradiation unit such as an LED (Light Emitting Diode) and a laser light source exposes the photosensitive drum, or an amount of drive power applied to the light irradiation unit. In the following description, the energy amount of the static latent image forming unit is referred to as an exposure light energy.
Further, the energy amount of the developing unit represents an energy amount defined with one of a developing voltage, a supply voltage, and a charging voltage. In the following description, the energy amount of the developing unit is referred to as a developing energy.
In the conventional image forming apparatus described above, when color balance is adjusted, first, different density detection patterns are printed or transferred to a surface of the photosensitive drum or a transfer medium. In the next step, a density detection unit formed of a density sensor and the like detects densities of the density detection patterns thus printed, so that one of the exposure light energy and the developing energy is controlled according to density values thus detected.
In this case, a correction value of a light amount is added to a printing condition, thereby controlling the exposure light energy. Alternatively, a correction value of a developing voltage is added to a printing condition, thereby controlling the developing energy.
In the next step, in the conventional image forming apparatus, the density detection patterns are printed on the surface of the transfer medium one more time. Then, the density detection unit detects densities of the density detection patterns thus printed, so that the other of the exposure light energy and the developing energy is controlled according to density values thus detected. Through the process described above, in the conventional image forming apparatus, it is possible to obtain proper color balance.
As described above, in the conventional image forming apparatus, when color balance is adjusted, first, one of the exposure light energy and the developing energy is controlled according to the density values. After one of the exposure light energy and the developing energy is controlled, the density detection unit detects the densities of the density detection patterns, so that the other of the exposure light energy and the developing energy is controlled according to the density values.
In this case, in the conventional image forming apparatus, depending on which one of the exposure light energy and the developing energy is controlled first, a final energy correction amount may be different. When one of the exposure light energy and the developing energy is controlled first, the other of the exposure light energy and the developing energy may be controlled by an amount different from the case in the reversed order.
As described above, in the conventional image forming apparatus, when one of the exposure light energy and the developing energy is controlled in a fixed order for adjusting color balance, color balance may be over adjusted. In other words, the light amount or the developing voltage may be adjusted by an excessive correction value. As a result, the conventional image forming apparatus may cause a print quality problem, thereby deteriorating printed image quality.
In view of the problems described above, an object of the present invention is to provide an image forming apparatus capable of solving the problems of the conventional image forming apparatus. In the present invention, it is possible to prevent color balance from being overly adjusted, thereby preventing image quality from deteriorating. Further, an object of the present invention is to provide a method of adjusting color balance applied to the image forming apparatus.
Further objects and advantages of the invention will be apparent from the following description of the invention.